1. Field of the Invention
This invention relates to a semiconductor laser, and in particular to an array-like semiconductor laser (hereinafter referred to as the array laser) comprising two or more semiconductor lasers integrally provided on a substrate.
Heretofore, the array laser of this type has been arranged as shown, for example, in FIG. 1 of the accompanying drawings. In FIG. 1, reference numeral 21 designates a support member formed of a silicon substrate or a copper block. An array laser 22 and a photodetector element 23 are disposed on the support member 21 so as to comprise individual lasers 22a-22e. In this example of the arrangement, the lasers 22a, 22b, 22c, 22d and 22e are successively turned on and the light outputs thereof are received by the photodetector element 23 so that the intensities of currents introduced into the respective lasers 22a-22e are adjusted in accordance with the intensities of the lights therefrom.
In the example shown in FIG. 1, there is a photodetector element, but an array-like photodetector element (hereinafter referred to as a photodetector element array) can be used.
FIG. 2 of the accompanying drawings shows an example in which a photodetector element array 33 is employed. In this example, an array laser 32 and the photodetector element array 33 are disposed on a silicon substrate 31 so as to face each other. The array laser 32 is bonded onto the silicon substrate 31, and the outputs of lasers 32a-32e are inputted to the photodetector elements 33a-33e of the photodetector element array 33 monolithically formed on the substrate 31. In this case, the laser lights outputted from the active layers of the lasers 32a-32e pass through the space into the photodetector elements 33a-33e.
The above-described semiconductor lasers according to the prior art suffer from the following disadvantages:
(1) Particularly, in the example shown in FIG. 2, the outputs of the adjacent lasers other than the outputs of the corresponding lasers are also input to the respective photodetector elements and these produce noise. For example, as regards the light input to the photodetector element 33b, the output from the laser 32b is of course the largest, but the inputs from the lasers 32a and 32c are also substantial and accordingly, it is difficult to detect the inputs from the lasers 32a-32e by the photodetector elements 33a-33e without mutual interference.
(2) It is difficult to install the lasers of the array laser or the array laser on the substrate so as to exactly face the respective photo-detector elements of the photodetector element array or one photodetector element.